IR presence detector (e.g. for model railway trains) PUBLIC

Provides a presence detector for model railway trains and similar moving things, providing an input to Arduino microcontrollers.

Provides a presence detector for model railway trains and similar moving things.

With model trains, D1 and D2 are best used embedded in the track, with reflectors glued to the underside of selected rolling stock. There will normally be very little infra-red light falling on the photo transistor, so the sensor will read nearly 5V. When a reflective item passes nearby, the transistor will conduct so the sensed voltage will fall to nearly zero.